The invention refers to a material and component testing machine for producing random length bending and/or torsion loads in preferably bar-shaped test samples.
Material testing machines of the type in question are already known in various designs. Here the clamped, bar-shaped test sample is caused to rotate by a drive motor, where it is subjected to a bending and/or torsion load. All known testing machines have the following disadvantages:
With most of the machines, a torsion load in connection with a rotating bending load is not possible. Random length bending load runs, that is, load runs which have loads randomly variable in time, cannot be carried out as the load run usually follows a sinusoidal function and the mean stress of the rotating bending has the value zero. As the test sample has to be caused to rotate and for the overlay of a torsional load, a relatively large apparatus expenditure has to be provided, bearing friction and balance errors coming from production inaccuracies give cause to incorrect test results. The bending moment acting on the test sample is not measured in the direct vicinity thereof, rather from lever arms and a remote applied force. Deviations in the lever geometry and last moments in the force transmission lead to incorrect test results. Tests with already cracked test samples cannot usually be carried out, rather they lead to vibrations in the machine and to useless results due to the asymmetry of the crack.
Furthermore the constructive design of many test machines results in awkward and time consuming change-over of the test sample. Also the measurement value transmission from the rotating shaft to the control and inspection devices is erroneous and subject to deflects.